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Rhydon is a large, gray, bipedal Pokémon with features of both dinosaurs and rhinoceroses. It has a cream-colored, drill-like horn on its snout. The female will have a smaller horn than the male. There are other protrusions on the head as well, including a spike curving forward from the middle of its head, two triangular, point resembling ears to the sides of the spike, a wide, wavy crest under the ears, and spiky ridges on its cheeks. It has red eyes and two fangs protruding from its upper jaw. It has a cream-colored stomach and a row of spikes down its back. Rhydon has a long tail with skinny, black stripes.
Rhydon is a physically powerful Pokémon. It is recorded as being able to topple buildings with a sweeping blow of its tail, and its horn is able to bore through solid rock and shatter diamonds. Rhydon is protected from heat and physical blows by its armor-like hide. It is stated to be capable of passing unscathed through streams of magma and withstanding a direct blow from a cannonball without being harmed. However, because of this tough hide, it is insensitive. Rhydon has a well-developed brain, but can also be forgetful. It lives in rough terrain.
According to interviews with Ken Sugimori (translation), Rhydon holds the distinction of being the first Pokémon ever created. This is further supported as its index number is 001 in Generation I, as well as early sketches from Capsule Monsters featuring Rhydon.